31 March 2011

The "One that Got Away" - edited

Ten years ago this month, in March 2001, Mike Turnbull and I were in the HKBWS Boardwalk hide on a hazy Saturday afternoon. The tide had receded and a Lesser Frigatebird was harassing all the other birds in Deep Bay. It was the focus of our attention - as you might expect.

Out in the middle of the bay, 300 to 400 metres away, the Frigatebird disturbed another bird from the surface of the water. Not another Shoveller, not even a duck, it flapped languidly in our general direction on long dark wings. Mike exclaimed " It's a Gadfly Petrel !! " with possibly an expletive or two. I knew I'd seen some members of this family in New Zealand, but was also acutely aware that I knew practically nothing about Pterodroma petrels.

I had about six frames of slide film left in the camera and, with a 1.4 converter on the old 600mm Pentax I was focussing manually. I was desperate to get a record shot, but knew the bird might come closer, too. Grab a shot now, or wait till later ? Suppose it just flies away ? In the end, I took only three shots, and this is the sorry "best" of them.

Mystery Pterodroma

The "Pterror" came to with 100 metres and crossed the line of mangrove to our left and was not seen again.

Mike T. circulated the photos and a description to solicit opinions on identification overseas, especially to Australia and NZ experts on pelagic birds. However no consensus could be reached and the record languished, the bird not identified to species, although there seemed to be agreement that it was a Pterodroma petrel of some sort, and eventually the HKBWS Records Committee accepted it as such.

For a birder the key point is that ANY member of this family is a "First" for both Hong Kong and mainland China.

In one of my Japanese photo books I saw a photo of Providence Petrel (Pterodroma solandri), and thought "That's it !" (Not very scientific, I know.) And after ten years no-one else seems to be convinced.

In 2007 I got a copy of "Albatrosses, Petrels and Shearwaters of the World" by Derek Onley and Paul Schofield. Looking at Plate 16 - Dark Pterodroma Petrels of the Pacific - I have become an "instant expert". A lack of white shafts on the upperside of the primaries should eliminate Kermadec petrel and Kermadec and Providence seen most likely on range. BUT other Pterodroma petrels may be possible, too, such as Murphy's and Herald.

But are mystery petrels really vagrant, or are we just not spending enough time looking in the right places ?

We can't alway identify everything we see and it is a pity that we couldn't really nail this one down. But Identification criteria are certainly improving all the time, especially with the widespread availability of digital photographs.

Who knows, perhaps one day we'll be able to work this one out. For now, - like a fishing story - it is "The Big One That Got Away " !

(Added 1st April 2001) - but I'm not fooling !

David James has kindly taken the trouble to comment on the photo above on the Oriental Bird Club internet news group as follows : -

"John Holmes has posted a photo of a Pterodroma on his blog that was photgraphed in Deep Bay 10 years ago. http://johnjemi.blogspot.com/
This bird is clearly a Herald Petrel, P heraldica. Only 5 petrels show a dark crescent in the white underwing flash (formed by the dark tips to the primary coverts). Solander's Petrel and Henderson Petrel never show a white belly or throat. Trinidade Petrel has dark lores. Kermadec is the most likely alternative, but its best feature, white primary quills, is not visible in ventral views. Other important details on the inner underwing are not clear.
However, the shape fits only Herald Petrel (and Trinnidade): a long and slim tail, and a skinny looking head. This is quite wrong for Solander's and Kermadec.

It is an intermediate morph bird, although there is little difference between pale and intermediate.
If you have Harrison's 1987 photo guide, look at p 56. If you have Onley & Schofield look at Plate 20, image 2c.

David James
Sydney"

For the record, then here are scans of all three photos I took in March 2001.

4 comments:

One of my photos had the yellow on a rare wood warbler photos so over-exposed that "armchair birders" were calling it something completely different... until other birders came and got better photos.

I do see the big bill and long pointed tail, double white patches in the primaries. Could be a Solander's. But then I think there is no doubt about the Canada petrel being a Solander's, too. Of course, now I'm the armchair birder, having never seen one in life (only a very few seabirders ever have).

"I don't think you need to call this bird a mystery petrel. The extra photos and the enhanced photos strengthen the case by indicating (if not proving) that the the inner underwing has a white leading edge and a tapering white bar at the base of the secondaries. A second photo confirms the long tapered tail and the funny head shape.

I understand the ID was widely discussed back at the time, and there were many opinions thrown about that I have not read. However, on body plumage this can't be a Solanders, Hendersons or Murphys. On shape it cant be a Slanders or Kermadec, and I presume not a Murphys either, but I haven't seen that species and the literature does not get to the point. It therefore has to be a Herald or a Trinidade (Round I) Petrel. It's the wrong ocean for Trinidade and it pale lores.

This is not hard. Perhaps exotic and unexpected, but not hard. I don't see why it has remained unidentified for so long. Are there any counter arguments to Herald? Has a case been mounted for the records committee?"

Taken with permission from an Email by David James.

David James is an Australian birder who went on his first pelagic off Sydney in 1982 and has been a seabird "tragic" ever since. As well as hundreds of day pelagics, he has been on shipboard surveys in the Southern Ocean, South Pacific, North Pacific, Indian and North Atlantic oceans. He has studied frigatebirds, tropicbirds and boobies at nesting sites on Christmas Island and in the Coral Sea. David has written advanced identification articles on frigatebirds (BirdingAsia 1: 22-38), gulls and Australian honeyeaters, and he prepared plumages accounts for about 100 species for the acclaimed Handbook of Australia New Zealand and Antarctic Birds. He has been a member of the Birds Australia Rarities Committee (on and off) since 1989, and has provided expert opinions on seabird identification to the California, Texas and Washington state rarities committees in the US. David has field experience over many years with Providence, Herald and Kermadec Petrels off eastern Australia.